It is known to use calcined clay as a clinker substitute for making cement or otherwise combining with cement, which is the binder that holds together aggregates in concrete and mortar compositions. The following patents provide examples.
U.S. Pat. No. 4,642,137 of Heitzmann et al. taught a binder composition that included portland cement in combination with metakaolin and at least one material selected from fly ash, calcined shale, and calcined clay, among other components.
U.S. Pat. No. 5,626,665 of Barger et al. taught cementitious systems comprising gypsum, calcined clay, and clinker consisting essentially of hydratable calcium silicates. The systems of this invention were described as having a water demand of less than about 33% nc (normal consistency); one-day strengths of at least about 1000 psi; and low alkali functionality. By increasing the amount of calcined clay, the resulting cementitious system was believed sequentially to gain alkali non-reactiveness, alkali resistance, and low chloride permeability.
U.S. Pat. No. 8,906,155 of Gasafi et al. taught a method for producing a clinker substitute which included pre-drying clay with an iron content greater than 1.5 wt-% to a moisture level of less than 10 wt-%, comminuting the clay to a grain size of less than 2 mm, calcining it in a furnace at 600-1000° C., and then cooling the resultant material.
U.S. Pat. No. 9,212,092 of Herfort et al. taught a cementitious composition having portland clinker cement and supplementary cementitious material which comprised heat treated clay and optionally heat treated carbonate material. The clay became substantially dehydroxylated while the optionally heat-treated carbonate material remained substantially carbonated; this could be accomplished by premixing the carbonate and clay before heating them to 400-700° C., or by heat-treating the clay separately to a temperature of up to 900° C. When the resultant compositions were used for cementing applications, they were believed to possess higher strengths. See also WO 2016/082936, CA 2968007.
EP3109216 A1 of Dominik Nied et al. taught that certain alkanolamines could accelerate the strength development of hydratable binders which included portland cement and clinker substitute materials including blast furnace slag, lime-rich and lime-fly ash, natural and artificial pozzolanic or latent hydratable glasses, and calcined clay. See e.g., paragraphs [0017] and [0019].